The present invention relates to the cracking of light hydrocarbons. In another aspect, the present invention relates to a method of increasing the conversion and in some cases the selectivity obtained during the cracking of light hydrocarbons.
It is well known that the product distributions obtained in the cracking of hydrocarbons are non-selective and, even at low conversions, produce a large number of primary products. Obviously, it would be preferable to obtain more selectivity to the specific desired products since such would give greater yields of the desired product and would in many cases make separation of the desired product less expensive.
In addition to poor selectivity, thermal cracking reactions are also known to require large inputs of energy to achieve high conversion levels. Accordingly, there is a need to increase the conversion level of such processes so that one can either use less energy or make more of the desired product in order to counterbalance the energy costs.
It has been known for several years that H.sub.2 S can change the conversion level of hydrocarbon pyrolysis reactions and alter the selectivity to various products. Theories for explaining the effect of the H.sub.2 S are presented in Scacchi et al, Int. J. Chem. Kinetics, 2, 115 (1970); Saige et al, C. R. Acad. Sc. Paris, 274, 322 (1972); Rebick, Frontiers of Free Radical Chemistry, Academic Press, Inc. (1980); and Rebick, Ind. Eng. Chem. Fundam, 20, 54 (1981). The present invention is based upon the discovery that the cracking of light hydrocarbons in the presence of H.sub.2 S and certain high surface area materials increases the conversion far beyond what one would expect from the effects of the H.sub.2 S or the high surface area material alone.